SrTiO3 (STO) thin films have been deposited on glass substrates by electron cyclotron resonance (ECR) ion beam sputter deposition at different substrate temperatures (100–600 °C). The structural characteristics of the deposited films show a transition from amorphous phase to polycrystalline phase at 600 °C. The films exhibit good transparency with an interference pattern in the visible region and a very smooth surface without cracks. The refractive index of the films increases with an increase of the substrate temperature, and their dispersion was analyzed by a single-oscillator model. The extinction coefficient of the films in the visible region is of the order of 10−3–10−2. The estimated values of the direct and indirect bandgap energies for the polycrystalline STO film are 3.80 and 3.32 eV, respectively. Its density is almost identical to the bulk STO single crystal, which is relatively high in comparison with those prepared by other techniques. The mechanical stability of the films is also improved with an increase of substrate temperature. Young's modulus and hardness of the polycrystalline STO film are 194.1 ± 15.5 and 22.5 ± 2.0 GPa, respectively.